Part timing is only he first problem. Now many employees will be juggling multiple part-time jobs and schedules. Many employers do not like employees with a second or third job. They want all of the employees focus on them. I've seen retail jobs or jobs with a probationary period demand 24/7 loyalty for 30-35 hours a week decades ago. I've seen other employers get upset at employees for so much as going to school at night on their own time.

The problem is with multiple jobs is that one bad day can cause you problems on two jobs. Transportation problems like car trouble or just a personal emergency OR appointment that requires a callout can cause trouble with TWO employers on the same day. Then I've had days where one job got upset at me because I could only work 3 hours overtime in a job that rarely gave overtime so I wouldn't be late for a part-time job that was going out of there way to document every absence AND lateness(once you were over 6 minutes late-write up).

The financial effects are bad enough let alone the logistics of a part timing work force.